The present invention relates to yttrium aluminum garnet fluorescent powders comprising a rare earth metal other than europium (Eu). The present invention also relates to the preparation of the yttrium aluminum garnet fluorescent powders and their use in a light-emitting device, particularly in a pink light-emitting device with high brightness.
Conventional fluorescent powders for use in pink light-emitting diodes are mainly produced by adding europium into crystal compounds (also named main lattice) such as Y3Al5O12:Eu3+ and Y2O3:Eu3+. Among them, yttrium aluminum garnet (YAG) has better light-emitting efficiency. The colors, i.e., chromaticity diagrams, of fluorescent powders can be controlled by changing the added amounts of europium. However, the variation range of color that can be controlled is small. II other words, it is difficult to control the concentration of the single luminescence center to obtain the desired chromaticity diagram.
Accordingly, fluorescent powders for pink light-emitting diodes without the above drawbacks and processes for the preparation of the fluorescent powders are highly desired.
The object of the present invention is to provide yttrium aluminum garnet fluorescent powders with formula (Y3-x-yZxEuy)Al5O12 or (Y3ZxEuy)Al5O12, wherein 0 less than xxe2x89xa60.8, 0 less than yxe2x89xa61.5, and Z is selected from a group consisting of rare earth metals other than europium (Eu).
Another object of the present invention is to provide a pink light-emitting device with high brightness, which comprises a visible or ultraviolet light-emitting diode as a luminescent element and a fluorescent body containing yttrium aluminum garnet fluorescent powders, wherein the diode emits a light with a wavelength ranging from 370 to 410 nm, and the light then excites the yttrium aluminum garnet fluorescent powders in the fluorescent body to emit another light with a wavelength ranging from 585 nm to 700 nm, so the two lights combine to produce a pink light with uniformly distributed colors.
Another object of the present invention is to provide a process for the preparation of the yttrium aluminum garnet fluorescent powders.